The Miami Dolphins fear that left tackle Jake Long suffered a season-ending triceps injury during Sunday's 23-16 loss to the New England Patriots, Jeff Darlington of the NFL Network reports.

Long was injured in the first quarter on Sunday and was observed on the sidelines wearing street clothes. While the No. 1 overall pick of the 2008 NFL draft is scheduled to undergo an MRI on Monday, team officials tell Darlington that the injury "doesn't look good."

If the worst fears are realized, and Long is out for the remainder of the season, Sunday may have been the last time the former Michigan standout suits up for the Dolphins. Long is in the final year of his rookie contract and is scheduled to be an unrestricted free agent in March. A multi-year extension that Long's representative -- Tom Condon of CAA Football -- would likely identify as a fair deal for his client is the seven-year, $84 million contract that Cleveland Browns left tackle Joe Thomas signed on Aug. 22, 2011. Thomas' deal contained $37 million in guaranteed money.

The Dolphins do have the option of using the franchise tag, but the high price of doing so may prompt GM Jeff Ireland to let Long test the free-agent market.

In previous collective bargaining agreements, the NFL franchise tags were determined by calculating the average of the top salaries at a particular position or position group, but that changed in the 2011 CBA. The franchise tags at each position from the last five years are now added up and divided by the league-wide salary cap numbers from the previous five years in order to determine a percentage, which is then multiplied by the salary cap for the upcoming season to determine the franchise tag number. As result, some franchise tag numbers, including those for offensive linemen, are trending downward.

If the league-wide salary cap number remains around $121 million, the franchise tag for an offensive lineman will be about $9.3 million. However, because Long's 2012 salary cap number ($12.8 million) exceeds the projected franchise tag figure, a secondary formula -- which sets the value of the tag at 120 percent of the players' previous year's salary -- remains in the CBA and could be Long's ticket to unrestricted free agency as it would cost the Dolphins $15.96 million in guaranteed base salary (and cap space during the 2013 offseason) to use the franchise tag on him.

The Dolphins used a 2012 second-round pick on Jonathan Martin, who played left tackle at Stanford but was viewed by many draft analysts as a right tackle prospect at the NFL level. Martin moved over to left tackle in Sunday's loss to the Patriots and may have an impromptu four-game audition protecting Ryan Tannehill's blindside. The results of the possible experiment could have a major impact on the Dolphins' approach to their 2013 offseason.